Saagar Jha > On Jan 17, 2018, at 16:56, Xiaodi Wu via swift-evolution > <firstname.lastname@example.org> wrote: > > On Wed, Jan 17, 2018 at 2:04 AM, David Sweeris <daveswee...@mac.com > <mailto:daveswee...@mac.com>> wrote: > > > Sent from my iPhone > > > On Jan 16, 2018, at 23:45, Jonathan Hull via swift-evolution > > <email@example.com <mailto:firstname.lastname@example.org>> wrote: > > > > Mainly semantics. > > > > We could technically use Int instead of having a Bool type (just using 1 > > and 0). We don’t do that since Int and Bool have intrinsically different > > meanings in code. > > > > What I am saying is that parameters that take the range 0 to 1 typically > > have a fundamentally different meaning (or at least a different way of > > thinking about them) than Doubles. It would be nice to be able to see that > > distinction when using APIs. > > > > With both this and the Angle type, I am pointing out areas where, due to > > historical reasons in C, we have conflated a bunch of types which have > > different behavior, and then just expect programmers to be conscientious > > enough to use them correctly in each case. These types/numbers all have a > > different forms of dimensionality. > > > > I’d like to discuss that before we lock everything down. > > +1 (although I think a “normalized to [0, 1]” type would be more useful than > a “percentage” type) > > Bool is not a good example; it permits precisely two logical values (0 and > 1). By contrast, if you're going to support 1000%, then your type supports > the same values as the underlying storage. As I wrote in a different thread, > one way to look at a type is the set of values that a variable can have. > > What is your limiting principle here if you think that a range that's not > enforced makes a value become of a different type? Often, a 1-5 rating system > is used. Sometimes, it's 1-4 or 1-10. And of course, a "3" on a 1-5 scale > means something very different from a "3" on a 1-10 scale. Should > ScaleFrom1To5 be its own type? And also ScaleFrom1To4 and ScaleFrom1To10?
Just a thought: if Swift ever allows integer literals in generics (e.g. for a fixed size array equivalent to C++’s std::array), this seems like how a type like ScaleFrom (and a percent type, for that matter) could be implemented. > > Besides, even supposing a percentage type would be in high demand, there's no > need for its inclusion in the standard library. It's very easy to implement > on your own in a third-party library. Moreover, custom operators will allow > you to define a postfix `%`, and then you could write: `let x = 100%`. Throw > in some heterogeneous arithmetic operators and you could do almost any math > you want. > _______________________________________________ > swift-evolution mailing list > email@example.com <mailto:firstname.lastname@example.org> > https://lists.swift.org/mailman/listinfo/swift-evolution > <https://lists.swift.org/mailman/listinfo/swift-evolution>
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